Switch



Dec. 24, 1946. D. G. CLIFFORD ETAI.

SWITCH Filed oct. s, 1942' 2 sheets-sheet 1 Dec. 24, 1946.

D. G. CLIFFORD ETAL SWITCH l Filed 0015. 8, 1942 2 Sheets-Sheet 2 INVENTORS .Q G-Cl/FF E C'. a/f/E'SS MW@ hm.

MAM ATTORNEY Patented Dec. 24, 1946 SWITCH David Gordon Clifford and Ernest C. Qkress, Montclair, N. J., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a

corporation of Pennsylvania Application October 8, 1942, Serial No. 461,336

8 Claims.

In its broader aspect, this invention relates to receiving and transmitting energy in the form of electro-magnetic waves and more specifically it relates to a novel switch which is connected between the transmitter and receiver and serves the purpose of protecting the receiver during the transmission pulse.

Use of reflection cf radio waves for various purposes, such as determination of altitude of an airplane to ground, for locating one airplane from ano-ther or from a xed situation, and for other purposes, is an acknowledged fact. The wave is generated, passed to the antenna and into space, reflects from the object addressed, returns to the antenna and thence to the receiver. A switch of automatic character has to be provided to keep the projected pulse from passing through the receiver at the time of projection but which will permit the reflected pulse to operate the receiver. Such va switch is now commonly referred to as a TR box.

The present invention is directed primarily to an improved TR box capable of use with a wave guide. The term wave guide is used to describe the means by which electro-magnetic energy is propagated in hollow tubes from one place to another before its ultimate transmission into free space, if that is to be done. More specifically, a wave guide includes the provision of a dielectric, such as air within a channel, the wave guide extending from place to place and constituting a metallic boundary laterally engirdllng the dielectric. The cross-sectional dimensions of the metallic boundary of the wave guide have a delinite relation to the character of the wave transmitted thereby. Literature has employed and this description will correspondingly employ the letter a to designate the short dimension and letter b to designate the long dimension of the cross section of a rectangular wave guide. In the present specification selection of a particular mode is employed for simplicity, and by arbitrary choice herein that propagation of electro-magnetic energy isi by means of the H01 wave. It is to be understood, however, that-other modes may be used and other shapes and" dimensions of wave guides maybe employed.

The degree of delicacy of operation of the TR box is highly important as itis essential that the high power of the outgoing signal shall notpa'ralyze or even filter through tothe receiver, and yet it is imperative that the faintest of reflected signals shall pass through the switch to the receiver. The present invention accordingly has for its primary object the provision of a switch or TR 2 box meeting the exacting requirements outlined above and with greater eiectiveness than accomplished by devices of the prior art.

More specifically, an object of the invention is to provide a TR box with a cartridge type electrode assembly.

Another object of the invention is to localize the lecessary evacuated region, and to require partial Vacuum only within the cartridge.

A further object of the invention is to provide a tunable TR box withthe electrodes and cartridge envelope maintaining an undisturbed relationship and with the partial vacuum undisturbed.

A still further object of the invention is to utilize moving parts for tuning purposes entirely outside of the cartridge.

Again, an object of the invention is to provide a cartridge construction which is readily removable and replaceable and necessitates minimum material and labor loss represented by the substitution.

Another object is to provide for proper orientation of the cartridge in the resonator and also to establish desired resonance mode.

Still further objects of the invention will appear as the description progresses, both by direct recitation thereof and by implication from the context.

Referring to the accompanying drawings in which like numerals of reference indicate similar parts throughout the several views:

Figure 1 is a sectional view longitudinally through a TR box and associated wave guide, as on line I-I of Figure 2;

Figure 2 is a sectional view longitudinally of the wave guide and transversely of the TR box, as upon line II-lI of Figure 1;

Figure 3 is an elevation of the cartridge structure utilized in our improved TR box;

Figure 4 is a longitudinal sectional view of a modified construction of cartridge;

Figure 5 is an elevation of the TR box or switch in its associated relationship with transmitting and receiving apparatus;

Figure 6 is a sectional View similar to Figure 1 showing a modified choke construction; and

Figure 7 is a cross section on line VII-VII of Figure 6.

In the speciiic embodiment of thev invention illustrated in said drawings, reference is rst made to Figure 5 wherein is illustrated the general assembly of apparatus comprising a wave generator i9 productive of high pulse energy of desired frequency promulgated as Hoi' waves longitudinally of a wave guide Il preferably of rectangular cross section. Such waves may be dlrectionally transmitted into free space directly from the wave guide or through the agency of an antenna, such as a horn, or otherwise. Preferably the waves are sent forth from a parabolic device, which for brevity and ease of reference will be termed an antenna I2 which can be moved about for directing the wave path o'r beam` in a desired direction and toward an object. The invention is preferably used in conjunction with.

ultra-high frequency radio waves, an advantage of which is the property of straight-forward pro'- jection and reflection in substantially the same manner as light waves. Accordingly, the projected wave energy directed toward some object, such as an airplane, reflects therefrom and on its return course between pulses is intercepted by the antenna I2 which concentratestheA wave to re-enter wave guide I I and travel therein and through a branch wave guide I3 to a receiver I4' which is then excited by the returned Wave. The generator is placed at a specied distance from the junction of wave guides II and I3 so as to present such an impedance at the junction (in the quiescent state) so as to divert the received energy toward the receiver in guide I3. Obviously the returned wave energy will be very weak as compared to the high power of the energy produced by the wave generator. The TR box I5 is interposed in branch wave guide I3 between the receiver and generator and between the receiver and the antenna to automatically prevent the high power energy from generator I0 during transmission from destroying or interfering with the receiver and yet permitting the receiver to be actuated in consequence of the relatively weak power of the returned' signal between pulses.

The switch or TR box of the present invention preferably comprises a cylindrical body of metal I6 which is hollow and in part provides a resonator chamber Il therein'. The body I6 is provided with a fixed end wall i3 which is situated in the plane of the long dimension wall b of the branch wave guidev I3, the said body I6 extending from 'said fixed end wall I8 of the wave guide, transversely through the hollow of the wave guide and out through the opposite long dimension wall b of said wave guide. Apertures, closed by windows I9 of material transparent to the wave energy are provided at parts of the resonator body within the wave guide and centered upon the center line of the wave guide. The windows are of suitable dielectric material, such as low loss glass and serve as means for passing the flow of wave energy in the guide through the resonator. i

Said windows are suitably dimensie-ned both as to diameter and thickness and with due consideration to their dielectric constant, to introduce a minimum of disturbance and still give sufficient coupling between the resonator chamber and the wave guide. These window apertures are shown circular, though they need not be, andrconcentric with a diameter of the resonator as well as with the center line ofthe wave guide. The windowed apertures are preferably as small as practicable ior still obtaining desired energy transfer without undue lessening of the surface continuity of the resonator. The area of the windows to a considerable extent controls the coupling coecient, detailed discussion of which is out oi.'` place here'. Since neither the resonator nor the. wave guide, in accordance with preferred construction, are evacuated, there is no need for the windows to be vacuum tight, and it is within the scope of the invention to omit the windows and leave theapertures open. Coaxial with and within the cylindrical resonator body is situated, in use, the removable and replaceable cartridge 20 constituting a feature of the present invention. The cartridge comprises essentially a long tubular envelope 2l Within which are situated cylindrical electrodes 22, 22 opposed endwise toward each other on a common axis and coaxial with the envelope. The outwardly directed ends of the elec# trodes are mounted upon lead-in wires 23, 23 of sufficient rigidity to maintain the electrodes in the position shown with a gap 24 between the inwardly directed. ends, said ends preferably being somewhat pointed. The glass of the envelope 2I is sealed around the lead-in wires, the envelope is evacuated, reiilled with ionizable gas if desired: to appropriate pressure, and tubulation 25 for. that purpose sealed oi. The cartridge is mounted to be removable in its entirety and replaceable at will, and in use should be situated symmetrical with respect to the center line of the wave guide,`that is, the centerline of the wave guide should be normal to and pass between the inwardly directed ends of the electrodes. The glass tube 20 is of adequate internal volume to maintain long life of operation.

Projecting outwardly from the fixed end I8 of the resonator body is an inverted cup 26 of cylindrical shape and having an outer end 2'Ifrom which'projects a neck 28. Said neck is coaxial with the' said cup which in turn is coaxially alined withv the cylindrical body portion I6. Said cup furthermore is provided with an axial bore for receiving one of the lead-in wires 23 of the cartridg'e. When the cartridge is adjusted to its desired position a set screw 29 projecting radially inward of the neck is employed for clamping the lead-in wire at such position. It will now be clear that insertion, removal, and replacement, as well as adjustment of the cartridge, may be readily eiected.

The bottom wall 30 of the resonator, that is. the wall opposite from the iixed end wall I8, is made adjustable. For that and other purposes said bottom wall is made integral with a cylindrical section SI coaxial with and spaced inwardly from the body portion I6, the hollow of this cylindrical section affording the necessary region for introduction of the cartridge to its desired position within the resonator. At the outer peripheral face of the said cylindrical section intermediate the ends thereof is a flange 32 the 4outer peripheral face whereof is screw threaded, as at 33, and is engaged with corresponding screw threads on the interior peripheral face of body portion I6. The outer end of the cylindrical section 3| is formed with a cap 34 thereon said cap having a rim portion 35 which overlies the outer peripheral wall of the body portion. Said cap constitutes a convenient finger hold by which the same may be manipulated and it will, therefore, be clear from the above that rotation of the cap will obtain a corresponding rotation of the cylindrical section and its threaded flange thereby advancing or retracting the movable end wall 3l] depending upon direction of rotation. Movement of the adjustable end wall 3B is for purposes of tuning the resonator.

Electrical continuity is necessary between the adjustable wall 30 and the cylindrical wall of the resonator, but sliding contact at the periphe'ry of the said end wall is highly objectionable. The construction employed accordingly spaces the periphery of the adjustable end wall slightly inward from the surface of the body portion of the resonator, leaving a gap 36 thereat. From the peripheral edge of the adjustable wall next the said gap, a skirt 31 projects rearwardly from the resonator said skirt being cylindrical and having a depth equal to a quarter wave length in the medium involved, which in the present showing is air. The adjustable wall 3B and skirt 3l accordingly constitute a piston, opening away from the resonator and setting up a high impedance at the open end. In consequence of the quarter wave length depth, high impedance at one end results in low impedance at the other end so that there will be low impedance at said gap 36 which wave energy recognizes as equivalent to contact between the surfaces and, therefore, constitutes electrical continuity without actual contact. This construction is referred to herein and in the trade as a choke.

yElectrical continuity between the adjustable wall 30 and its adjacent electrode 22 and between the fixed wall I8 and its adjacent electrode 22 is obtained by a choke in a manner similar to that above described with respect to the adjustable wall and resonator body. The construction of choke accordingly provides a metal ring 38 for the xed wall I8 and a metal ring 39 for the adjustable wall 30 of the resonator, both said rings projecting outwardly from the resonator and having an inside diameter of appropriate size for permitting the cartridge to loosely pass therethrough. Ring 38- is likewise smaller than the cylindrical wall of cup 26 so there is an annular space therebetween. This space is iilled with a glass or other dielectric ring 4I) having the same loss tangent and real dielectric constant as the glass of the cartridge envelope. Similarly, ring 39 is spaced inwardly from cylindrical section 3l leaving an annular space therebetween which is lled with a glass or other dielectric ring 4I also having the same loss tangent and real dielectric constant as the glass of the cartridge envelope. Each metallic ring 38 and 3,9 has an axial depth equal to a quarter wave length in the medium employed, which in the present instance is glass.

Observation is made at this time, that the wave length in a dielectric such as glass is materially shorter than in air, and in the present showing, length of the metallic rings 3B and 39 represents a single quarter wave length for the glass dielec- 5'1 tric as compared with the depth of the piston wall or skirt 31 heretofore described which represents a single quarter wave length in air. As explained above, high impedance at an open end means there must be low impedance a quarter a wave length distant where the rings are attached to their respective end walls, wherefore, for the wave energy involved, there is electrical continuity thus obtained between the said end walls and the adjacent electrodes at the ends adjacent to le' the resonator I1. It may be here added that all parts above described, except those specifically referred to as glass or dielectric, are of suitable metal such as brass, copper and the like, to be electrically conductive.

In 'performing its function as a TR box, the resonator is constructed and positioned with respect t0 the junction of the wave guides II and I3 so as to present such, an impedance at the junction to provide electrical continuity through the guide ,II during transmission and prevent leakage of power above a safe value to the receiver and furthermore to provide a suitable im.- pedance at the junction during the period of reception (generator quiescent) so that the received energy ycan pass substantially unattenuated to they receiver. In greater detail this means that some spark mechanism is placed inthe resonator which is ineiective during small signals or small pulses and allows the energy to pass through substantially unattenuated. On the other hand, however, during the time when the generator l0 is operating and/or a large pulse is received, the spark gap discharges, reducing the Q of the resonator, and blocks the large signal there, cutting down the transmission through the TR box to protectiveV values; This discharge occurs during the high pulse because a very high electric gradient is set up between the spark gap electrodes properly positioned in the resonator. The use of such a spark gap in the cylindrical resonator containing the sparkgap electrodes coaxial with its axis will not permit an easy cornputation of the resonant frequency of the system.

As 'it'has been found that there is a time lag, innitesimal though it may be, in the high elds becoming effective to break down the gap between electrodes 22,22 it becomes deiinitely desirable to obtain greater promptness in this respect. Generally speaking for the moment, this objective is attained by utilizing an ionizable gaseous mediumin the resonator and a keepalive therein by which a gas ionization is maintained and thereby supplying the desired ionizing radiation across the gap. Consequently when resonant potential builds up across the gap the moment of breakdown of the gap is accelerated, thus reducing the time lag in operation. Accordingly, the resonator body is rst evacuated after which approximately one millimeter (or more if desired) of an appropriate gas is. admitted. Suitable gases for the purposes include hydrogen, nitrogen, with or Without water-Vapor, as well as other gases alone or in combination.

For keep-alive purposes, one of the electrodes is rendered emissive. As. shown in Figures 1 to 3 the inner end of one electrode has aradio-active or gamma emission' material thereon, such as radium, as indicated yat 41.'

`Otheri'formsof keep-alive electrode may be provided, and in Figure 4 is shown a construction wherein glow discharge is obtained by a structure utilizing external potential for the purpose. Some rn'odiilcatior of the envelope is likewise involved. In this showing oneelectrode 22' dii"- fers `from electrode 22 in that it is hollow or tubular and has therein a rod or wire 42 which is a continuation of its lead-in wire 23. This rod extends to the forward end of electrode 22 so as to be at the forward opening of the electrode but without making contact therewith. Rod 42 may be of electron emissive character, such as tungsten-oxide-barium, tungsten-barium, strontium-barium and the like. The envelope 2 I next the tubularelectrode 22' is sealed to a metallic tube 43 of substantially the same diameter and the electrode 22 is anged as at 44 next its outer end so` asy to fit this metallic tube for support and centering thereby. The flange 44 may be secured in place within the tube by soldering as at 45. Beyond the ilange the lead-in wire 23 is sealed within the metallic tube by a glass bead 46. Potential diierence between the tubular electrode and the rod 42 may be applied through the metalf' I' lic sleeve 43 and the lead-in wire 23.

In the foregoing description, it will be vobserved that an important lfeature is the provision of quarter wavelength of coaxial lines by metallic rings 38, 39 in conjunction with the electrodes 22, to secure eiective' electrical connection through the glassv of envelopev 2ll at the desired placche-- tweenthe electrodesand the body of the, resonant; chamberV l 1. The structure thus far described has the advantage of overall limitations of length by use of relatively short chokes by virtue ofthe hollows of the chokes being filled with the dielectrics 40 and 4l .with the dielectric the same, or having the same dielectric constant, asV the glass or wall of envelope 2|. The inclusion of glass as dielectric rings 39 and 40, however, introduces certain difliculties in fabrication, dueto the nature of the material and the desirability of' obtaining a snug fit thereof in its appointed place. It is accordingly deemed within the scope of the invention to utilize other dielectricA than glass, and to vary the arrangement of the choke if found desirable. A modified construction in this respect is accordingly shown in'Figures 6 and 7.

In connection with the construction shown in Figures 6 and 7, those parts which are identical with parts heretofore describedA are identied by the same reference numeralsand repetition of description thereof is omitted. As to parts which are similar, the same reference characters with the addition of the` letter a thereafter are applied and the following description will set forth the differences so far as deemed necessary.

Metallic rings 39a andv 40a are provided in this modified. construction of Figures 6 and 7, said rings having a quarter wavelength dimension axially thereofY as in the previously described construction, but in this instance said rings do not provide hollow spaces to the next adjacent surroundingV wall, but are solid from their inner openings to said surroundingv wall.

Axially` outward from each said ring 39a and 40a is a choke, each being constituted by a longitudinal cavity 48 having a quarter wavelength dimension. in the axial direction, the wavelength dimension being referred to the dielectric of the cavity, in this instance, in air. Said cavityy in each instance has acircular slot opening or gap 49 at the end next the metallicring and inwardly toward the cartridge or envelope. (The effect of this choke isto introduce a high'impedance at the gap dsthereby forcing a low impedance at the. far end therefrom ofY the metallic ring, namely at the end of the metallic, ring next the resonator chamber.) Thus, both constructions obtain this desired low impedance across the gap and provide the eiect" of electrical continuity between the electrodes andthe adjacent wall of the resonant chamber.

The constructions sho-wn are accordingly both of cartridge types, namely, longn and slender and representing a minimum ofl evacuated volume. The cartridge can be insertedfat, the resonant chamber of the-TR box, which chamber no longer has to be of partial.vacuumtypeconstruction as inthe prior art. This isextremely-important because oftheprecisicn of part fabricationlrequired ofthe resonant chamber ofthe TR boxpand the resulting high cost. anddiiflculty of fabrication ifeach TR box is made as a comp-leteand evacuated` integral unit; With a- TR. box of the present invention', any failure. of' partial vacuum or of the discharge electrode characteristics; can be readily repaired or altered by simplyf inserting a newv cartridge. It furthermore may be pointedout that an outstanding featurerof* the-:device ofthe present invention is the abiiity tV arbitrarily-sclectf gap width for optimum operation and this gap will then be independentfofthe wavelengthcontrolling mechanism. More-specifically, it: is to beA noted that tuning by rotation ofcap 35 does not affect the gap 24 between the electrodes` at. all.

Since the various details of construction, asf

out departing from the inventive concept or scope of the invention, it is intended that all matter contained in the specification or illustrated in the drawings, shall be interpreted as exemplary and not in a limiting sense. t is also to be understood that the following claimsA are intended t0 cover all of the generic and specic features cf the invention herein shown and described and all statements of the scope of the invention herein set forth as aL matter of language which might be said tofall therebetween.

We claim:

l. A 'IR box comprising a non-evacuated enclosure forming a resonant chamber having a cylindrical side wall, and said side wall having window openings to the exterior of said chamber, and a cartridge structure insertable through said chamber, said cartridge structure comprising a partially evacuated envelope and electrodes separated by a gap within said partially evacuated envelope, said gap being substantially opposite said window openings.

2. A TR box comprising an enclosure forming a resonant chamber having opposed end walls provided with openings therethrough, a cartridge structure traversing said chamber past said. opposed end walls and projecting through said openings, said cartridge having electrodes therein, and means next said openings outside said end walls for establishing electrical continuity between said end walls and electrodes while maintaining physical separation thereof.

3. A TR box comprising an enclosure forming a resonant chamber and having a cylindrical wall, a movable wall to said chamber for tuning to desired resonance, said movable wall being spaced from the said cylindrical wall, means for establishing electrical continuity across said space, and a cartridge structure having a dielectric envelope in part within said chamber and having electrodes therein separated from each other by a gap -andadapted to destroy resonance in said resonant chamber, one of said electrodes being in part within said movable wall and the envelope being interposed in part therebetween, and means for establishing electrical continuity between one electrode and said movable wall through said dielectric of the envelope at the said part thereof interposed between said one electrode and movable wall.

4. A TR box comprising an enclosure forming a resonant chamber and having a cylindrical wall and end walls of which one is adjustable in an axial direction of the cylindrical wall, said movable wall being spaced from said cylindrical wall, means for establishing electrical continuity across said space, a cartridge structure having a dielectric envelope in part extending through said end walls and in part within said chamber and having electrodes therein separated from each other f by a gap, said electrodes projecting in part through said end walls within the envelope and the envelope being in part interposed between said electrodes and said end walls, and means for establishing electrical continuity through said interposed part of the envelope between each said electrode and-the said end wall through which each electrode projects.

5. A TR box comprising an enclosure forming a resonant chamber and having a cylindrical wall and end walls of which one is adjustable in an axial direction of the cylindrical wall, an electrode cartridge supporting means projecting from the xed end wall, and supporting and adjusting means projecting from the movable end wall, both of said end Walls having openings axially therethrough for receiving an electrode cartridge inserted therethrough, both of said end walls having quarter Wavelength rings neXt said openings projecting outwardly from the resonant chamber for establishing electrical continuity at said openings with electrodes situated therein,

6. A TR box comprising an enclosure forming a resonant chamber, a cartridge structure insertable through said resonant chamber, said cartridge structure having electrodes each passing through a different wall of said enclosure, and means for establishing electrical continuity through the cartridge structure from the electrodes to the respective walls of the resonant Chamber through which said electrodes pass, said means constitutingT a choke for said electrodes whereby Inode distribution is maintained in said chamber.

'7. A TR box comprising an enclosure forming a resonant chamber, a cartridge structure insertable through said resonant chamber, said cartridge structure having electrodes each passing through a different wall of said enclosure, means for establishing electrical continuity through the cartridge structure from the electrodes to the respective walls of the resonant chamber through which said electrodes pass, said means constituting a choke for said electrodes whereby mode distribution is maintained in saidv chamber, said choke comprising a metallic ring and a solid dielectric around said ring of a length equal to a quarter Wavelength in the dielectric.

8. A TR box comprising an enclosure forming a resonant chamber, a cartridge structure insertabie through said resonant chamber, said cartridge structure having electrodes each passing through a different wall of said enclosure, means for establishing electrical continuity through the cartridge structure from the electrodes to the respective walls of the resonant chamber through which said electrodes pass, said means constituting a, choke for said electrodes whereby mode distribution is maintained in said chamber,v said choke comprising a metalli-c ring having longitudinally therebeyond a circular gap toward the cartridge and providing a longitudinal cavity communicating with said gap and extending longitudinally away from the said ring with a length equal to a quarter wavelength in air.

DAVID GORDON CLIFFORD. ERNEST C. OKRESS. 

